(1) Field of the Invention
This invention relates to a pressure sensor used inside a container. The present sensor firstly sets a predetermined pressure as a reference, not the atmospheric pressure, for providing information about any pressure change inside the container.
(2) Background of the Invention
The sensor mostly used now can measure a pressure or a pressure difference/signal to users for taking necessary steps only through comparing with the well-known standard pressure, i.e. the atmospheric pressure. The sensor applied in an air compressor is also one of this kind. Take the example of the air compressor for a painting gun (referring to FIG. 1). As talking about the painting gun, people will definitely think of paint spraying. For achieving a good spraying, the ratio of air to paint is a key point, and the quantity adjustment of the air for obtaining a substantial pressure level is another key point.
When the compressor (1) works, the pressure sensor (11) will be prepared separately and then be connected at one end thereof with the indicator (12) through a pipe. Moreover, another end of the pressure sensor (11) is remained opened to the ambience, by which the outside pressure can be obtained as a standard pressure to measure the pressure inside the air compressor. The indicator (12) will show the pressure or the pressure difference through an electric signal for the users to control the pressure of painting gun.
Aforesaid kind of pressure sensor with a connection with the outward can measure an inside pressure by comparing with the standard pressure (around 1 unit of atmospheric pressure) and show it to the indicator. Because the standard of atmospheric pressure might vary with the weather, the measurement result will be fluctuated as well. Besides, there is a pipe on the sensor""s open end to the outward, so that possible leakage may happen if the joint structure is not well sealed.
Accordingly, the inventor proposes the solution techniques and methods as follows.
The pressure sensor inside the container is actually a shell with protrudes respectively located thereof at a top end, a bottom end and a middle part for clipping a body of the sensor. There is an air chamber, formed between a bottom plate and an inside wall, for providing thereinside an air-tight chamber with a spring located at the center of a base of the airtight chamber. The spring supports against and is covered by a button at the top, which then is covered by a pressure membrane. A round air-tight cushion is set on the bottom against the membrane. On the pressure membrane, another chamber is located, through which the pressure inside the container can be conducted. In the middle of the chamber, there locates a shaft with a movable protrudent shaft for contacting the pressure membrane. A plurality of electric conductive points is facilitated to both insides and outsides of the shaft for further linking with respective electrodes on the base plate fixed beyond the shaft. At least an air hole is used to penetrate the base plate and is connected to the air chamber.
In the present invention, the reference pressure for the pressure sensor is a fixed value. When the pressure inside the container is equal to the reference one, the pressure membrane and the protrudent shaft will not move. Upon that the electric conductive points on the shaft do not touch the protrudent shaft, the electrodes will not be conducted and no signal can be generated to the users. When the pressure inside the container is greater than the reference pressure, the pressure membrane as well as the protrudent shaft will move downward. Because the electric conductive points on the shaft are not touched by the protrudent shaft, so that the electrodes will not be conducted and no signal can be produced either. When the pressure inside the container is less than the reference pressure, the pressure membrane and the protrudent shaft will move upward. In this situation, the electric conductive points on the shaft will be touched by the protrudent shaft, so that the electrodes will be conducted for producing a signal to inform the users to take some necessary steps.
In the present invention, the pressure sensor in the close container is not air-communicated with the outward through any pipe, so that the reference pressure will not be affected by the atmospheric pressure. Therefore, the measurement result provided by the pressure sensor of the present invention can be relatively reliable.